I made a living as a photographer for 10+ years, I have owned most lenses from both Nikon and Canon at some point (as well as Hasselblads and Leica's)
16mm up to and including the Canon 600mm . I shot pro sports for years as well as high end weddings and other fun stuff.
You're not going to have the opportunity to "test drive" either a Nikon or Canon long enough to make a fair descision. That being said ( and it's been stated by a few people here already ) . It's more about understanding the tool your using, learn the camera inside and out.
Next is the quality of the lens. Any kit lens is a piece of crap. The longer the zoom the more plastic inside the lens. That means the light is bouncing off all of those elements made of plastic. This is not a good thing !
Yes , a kit is a great way to get started, but you're really getting cheap stuff in a kit. Consider buying a body , and possibly a body that is a step above the kit body.Entry level is always going to be poor quality and will always have that cheap feel to it .
Look at one that comes with a metal body to lens mount not a plastic one. The same goes for the better quality lenes. They have metal mounts not plastic.
If you buy a cheap lens, don't put a UV filter on it, you just putting plastic on top of plastic. When you spend money on a good lens , then you get a quality glass filter for $100 to protect your investment.
I'm also not really a big fan if the image stabilaztion lenses. I believe it's really just a way to jack up the price and that it doesn't really do what it supposed to do. With time you will learn to properly hold the camera and control your breathing if and when you need to take ahand held picture at 1/15 of a second. Not to many people have a need for this.
Hold the camera in your hand, try to get a feel for the buttons , display and the ease of use of the common features you'll utilize. I highly doubt you would hate either a Nikon or Canon, but everyone has an opinion. Mine is go with what feels right, but spend as much as you can and consider buying the items not as a kit but as individual pieces. You will spend more , but get better stuff.
You can't get everything all at once, I'm a little out of the loop on the amatuer models, but consider starting out with a descent body and a quality 28-70 type of lens.With time you can add to you lens collection.
Enjoy you're search for a camera, take your time....
back in the day canon 600mm lens EOS- 1N ,both shot on Fujichrome 50
( slide film)
Shot with a 70-200 2.8 lens w/EOS-1D ( Digital )
Otiel Burbridge , bass player for the Allman Brothers
Gregg and Dickey Shot on Fuji 800 approx 1/30 sec at 2.8